1. Field of the Invention
The present invention relates generally to reticles employed in forming photo-lithographically patterned layers employed within microelectronics fabrications. More particularly, the present invention relates to non-absorbing anti-reflective coated (ARC) reticles employed in forming photo-lithographically patterned layers employed within microelectronics fabrications.
2. Description of the Related Art
Conventional in the art of microelectronics fabrication is the use of reticles which are employed with coherent light sources to print upon the surfaces of microelectronics substrates fine line-width features of microelectronics devices and conductor elements. Such reticles are typically fabricated from a transparent substrate having formed thereupon a patterned metal layer which defines the microelectronics device and/or conductor element features to be printed.
Although the optical characteristics of coherent light passing through conventional reticles are typically well defined and understood, occurrences occasionally arise in microelectronics manufacturing processes employing those conventional reticles wherein coherent light reflections from surfaces of those conventional reticles are undesirable. Such occurrences may include, but are not limited to: (1) coherent light reflections which impede proper alignment of reticles within semiconductor substrate photo-exposure tooling, and (2) coherent light reflections which impede proper patterning of photo-active layers which are patterned through use of those conventional reticles. The present invention is directed towards the goal of providing for use within semiconductor substrate photo-patterning processes and photo-exposure tooling reticles from whose surfaces there is attenuated or eliminated undesirable light reflections.
The use anti-reflective coatings (ARCs) to attenuate or eliminate undesirable coherent light reflections from the surfaces of reflective semiconductor substrates desired to be patterned while employing photo-lithographic processes has been disclosed in the art. Such anti-reflective coatings (ARCs) are typically formulated from organic polymer compositions into which have been incorporated dyes which absorb strongly at the coherent light wavelength at which light attenuation or elimination is desired. Such anti-reflective coatings (ARCs) may alternatively be formed either: (1) directly upon a reflective semiconductor substrate and beneath a photo-active composition which is employed to pattern that reflective semiconductor substrate; or (2) as a discrete layer within a multi-layer stack of photo-active compositions formed upon a reflective semiconductor substrate for the purpose of patterning that reflective semiconductor substrate.
For example, Wolf et al., in "Silicon Processing for the VLSI Era," Vol. 1: Process Technology, (Lattice Press: 1986), pg. 441 discloses the use of an anti-reflective coating (ARC) beneath a photoresist layer and directly upon a reflective semiconductor substrate when fabricating an integrated circuit upon the reflective semiconductor substrate. In addition, Fuller et al., in U.S. Pat. No. 4,557,797 discloses a metal layer patterning method which employs an anti-reflective coating (ARC) between the two layers of a bi-layer photoresist structure employed to pattern a metal layer which comprises a reflective semiconductor substrate of significant topography. The disclosed method provides an integrated circuit processing method operable upon the non-planar reflective semiconductor substrate topography with minimal additional processing steps and expense.
Although not specifically directed towards anti-reflective characteristics of reticles employed within microelectronics fabrications, there is also known in the art of microelectronics fabrication various styles and configurations of phase shift reticles which provide enhanced optical characteristics when employed for photoexposing photoresist layers employed in fabricating microelectronics fabrications. Examples of phase shift reticles, examples of methods for fabricating phase shift reticles and examples of methods for forming patterned microelectronics layers while employing phase shift reticles are disclosed, for example, by Rolfson, in U.S. Pat. No. 5,194,345; Kemp et al., in U.S. Pat. No. 5,292,623; Miyazaki et al., in U.S. Pat. No. 5,328,786; Dao et al., in U.S. Pat. No. 5,354,632; Rolfson et al., in U.S. Pat. No. 5,372,901; Reinberg, in U.S. Pat. No. 5,460,908; Tomofuji et al., in U.S. Pat. No. 5,589,305; Iwamatsu et al., in U.S. Pat. No. 5,609,977; and Mikami et al., in U.S. Pat. No. 5,614,336.
Desirable in the art of microelectronics fabrication is a reticle, and a method for fabricating the reticle, where undesirable reflections from the reticle may be attenuated or eliminated in order to assure optimal processing of microelectronics substrates upon whose surfaces are printed microelectronics device features and conductor element features through use of the reticle.